1. Field of the Invention
The present invention relates to a printhead. More particularly, the present invention relates to a nozzle plate and printhead that provide for control of a deflection direction of fluid ejected through a nozzle to improve a resolution of a printed image, and a method of manufacturing the same.
2. Description of the Related Art
Generally, a printhead is a device for printing an image on a surface of an object by ejecting droplets of fluid on a desired location of the object. A common printhead is an inkjet printhead that may print using a plurality of colors. Such an inkjet printhead may be classified, according to the method of ink ejection, into a thermal inkjet printhead and a piezoelectric inkjet printhead.
In the thermal inkjet printhead, ink is quickly heated by a heater, formed of a heating element, when a pulsed current is applied to the heater. The ink is heated until it boils and generates bubbles. The bubbles expand and apply pressure to ink filled in an ink chamber, thereby ejecting the ink out of the ink chamber through a nozzle in the form of droplets. Thus, in the thermal inkjet printhead, the heater functions as an actuator that generates the ejecting force for the ink.
In the piezoelectric inkjet printhead, a piezoelectric material is used as an actuator. A shape transformation of the piezoelectric material generates pressure, thereby ejecting the ink out of an ink chamber.
FIG. 1 illustrates a typical piezoelectric inkjet printhead. Referring to FIG. 1, a channel plate 10 is provided with an ink channel including a manifold 13, a plurality of restrictors 12 and a plurality of ink chambers 11. A nozzle plate 20 is provided having a plurality of nozzles 22 that corresponds to the plurality of ink chambers 11. A plurality of piezoelectric actuators 40 is disposed on the channel plate 10. The manifold 13 functions to supply ink from an ink storage region (not shown) to the plurality of ink chambers 11. The restrictor 12 functions as a channel through which ink is introduced from the manifold 13 to the corresponding ink chamber 11. The ink chamber 11 stores ink that is to be ejected. Ink chambers 11 may be arranged on one or both sides of the manifold 13. The volume of the ink chamber 11 varies as the corresponding piezoelectric actuator 40 is driven, thereby generating pressure variations to eject ink through the nozzle 22 and draw ink through the restrictor 12. In detail, a top wall (i.e., ceiling) portion of each ink chamber 11 on the channel plate 10 is designed to function as a vibration plate 14 that is deformed by the piezoelectric actuator 40.
The piezoelectric actuator 40 includes a lower electrode 41 disposed on the channel plate 10, a piezoelectric layer 42 disposed on the lower electrode 41 and an upper electrode 43 disposed on the piezoelectric layer 42. Disposed between the lower electrode 41 and the channel plate 10 is an insulating layer 31 such as a silicon oxide layer. The lower electrode 41 is formed on an overall top surface of the insulating layer 31 to function as a common electrode. The piezoelectric layer 42 is formed on the lower electrode 41 and is located above the corresponding ink chamber 11. The upper electrode 43 is formed on the piezoelectric layer 42 and functions as a driving electrode, applying voltage to the piezoelectric layer 42.
When an image is printed using the above-described typical inkjet printhead, the resolution of the image is significantly affected by the number of nozzles per inch. The number of nozzles per inch is represented by “Channels per Inch (CPI)” and the image resolution is represented by “Dots per Inch (DPI).” In the typical inkjet printhead, the improvement of the CIP depends on continuing improvements in processing technology. However, current trends in processing technology may not keep pace with demands for increasingly higher resolution images. Therefore, a variety of technologies for printing a higher DPI image using a low CPI printhead have been developed.
FIGS. 2 and 3 illustrate examples of technologies for printing a higher DPI image using a low CPI printhead. Referring to FIG. 2, a plurality of nozzles 51 and 52 are arranged along two or more rows and may be staggered. The array of the nozzles 51 and 52 may be used to print an image forming a single line. That is, dots 61, formed by the nozzles 51 arranged along the first row, and dots 62, formed by the nozzles 52 arranged along the second row, alternate on a print medium 60, e.g., a sheet of paper. In the illustrated example, the image DPI formed on the paper 60 is two times the CPI of the printhead 50.
However, in order to precisely print the image, the nozzles 51 and 52 must be arranged accurately along the respective rows. Therefore, this requires an alignment system that can precisely arrange the nozzles 51 and 52, which may increase the printhead size and cost.
In the example depicted in FIG. 3, printing utilizes a printhead 70, having a relatively low CPI, which is inclined at a predetermined angle Θ with respect to a print medium 80, e.g., a flexible substrate or a sheet of paper. The inclination of the printhead 70 results in the intervals between dots 81 formed on the paper 80 becoming less than the intervals between the nozzles 71 of the printhead 70. Thus, the DPI of the image printed on the paper 80 is higher than the CPI of the printhead 70. In this example, the greater the inclined angle Θ, the higher the DPI. However, the inclination of the printhead causes the printing area to be reduced so that the length of the printhead 70 must be increased in order to maintain coverage of the paper 80.